Research On FEM Modeling And Dynamic Characteristic Of The Submerged Buoy System

The submerged buoy system is a kind of submerged suspending structuremooring system, which has been used to obtain marine environment parameters suchas temperature, flow velocity etc. Along with the expansion of its application scope,acoustic signature also becomes a significant measuring parameter of buoy system,thus the requirement on its vibration character is rising.This thesis is aim to establish a kind of dynamics analysis method for thesubmerged buoy system, in order to realize high-precision forecast analysis, then,providing the reference method for research on vibration analysis and oscillatorycontrol technology of this kind of system.This thesis first discusses FEM modeling methods for the system. For mooringcable, BEAM188, LINK8and other FEM elements are considered respectively; forbuoy body, solid and mass elements are considered; the spring-mass model andtensile cable model are considered with regard to system. Since the system isunderwater, a detailed study on added mass is carried out, considering differences ofadded mass in various directions. After a series comparative analysis, the FEMmodeling for the submerged buoy system should be: beam element for mooringcable, solid element for buoy body. By comparing the frequency result from FEMmodeling and sea test, the accuracy of conclusion is testified.On the basis of analysis of FEM modeling mentioned above, the attitude andvibration transmissibility of the system is discussed in this paper. The attitude ofbuoy system is premise of its normal operation, and the vibration transfer pattern isthe basis of vibration control.Finally, this article has touched on vibration control of the system. Starting withamplitude and distribution of system frequencies, nylon and steel cable for mooringsystem are compared and the difference between whether the structure has tail isdiscussed. Calculation results show that nylon mooring cable and structure with notail is better, mainly because it better avoid measuring interference from systemnatural frequencies.